Lecture 6 Nucleation and growth of thin films and nanostructures

Physics 9826b
6.3 Nanomaterials growth methods
Two approaches
Top-down
Patterning in bulk materials by
combination of
Lithography
Etching
Deposition
- can be applied for variety of materials
- limited by lithography resolution,
selectivity of etching, etc.
Bottom-up
Structure is assembled from well-defined
chemically or physically synthesized
building blocks
Self-assembly
Selective growth
- require accurate control and tunable
chemical composition, structure, size and
morphology of building blocks
- in principle limited only by atomic
dimensions
11
Mechanical Methods (Mechanosynthesis)
Low cost fabrication: ball milling or shaker milling
Kinetic energy from a rotating or vibrating canister is imparted to hard spherical
ball bearings (under controlled atmosphere)
(1) Compaction and rearrangement of particles
(2) First elastic and then severe plastic deformation of
the sample material formation of defects and
dislocations
(3) Particle fracture and fragmentation with continuous
size reduction formation of nanograined material
1 KIC
E
F
~ ~
Y a a
F – stress level, when crack propagation leads to
fracture; - surface energy of the particle; a - length
of a crack
K
IC
Y
F
a
-material with defects with a wide distribution of size
Lecture 10 12
January 30 – February 4, 2013 6